1) Field of the Invention
The present invention relates to a signal transmission system and circuits therefor, and to an effective technique available in a signal transmission system and circuits therefor both of which perform the electrical connection between digital signal processing apparatus comprised of, for example, a CMOS (complementary Metal Oxide Semiconductor) or the like or between functional blocks thereof.
2) Description of the Related Art
As a system for performing the signal transmission at high speed between digital circuits made up of semiconductor integrated circuit devices, may be mentioned an ECL (Emitter-Coupled Logic) type interface system for transmitting a signal having small amplitude of 0.8 V or so. As an example of transmitting the signal having such small amplitude using CMOS circuits, there is known a technique described in the paper "CICC (Custom Integrated Circuit Conference)", p.p. 10.7.1-10.7.4, May 1989. Even in the case of the system for transmitting the signal having small amplitude, similar to the above one, there is also known a transmission system free of use of ECL level. As such an example, there is known a technique described in the paper "ICCD (International Conference On Computer Devices)", p.p. 344-347, Oct. 3-5, 1988.
An approach for rendering the processing operation of a CMOS circuit high-speed and bringing the CMOS circuit into high integration has been performed with advancement in a fine processing technique of semiconductor devices. With this practice, high performance has been achieved inside a semiconductor chip. However, an approach for rendering, high-speed, the signal processing of transmission circuits for performing the electrical connection between digital apparatus made up of semiconductor integrated circuit devices or between functional blocks thereof still remains backward. This is attributed to the fact that the current drive ability of the CMOS circuit is low and a signal-transfer delay time substantially becomes larger at a position where the capacitive load of the circuit is increased. Accordingly, a digital integrated circuit using a CMOS circuit has generally adopted a method for disposing bipolar ICs having large drive ability around the digital integrated circuit to thereby transmit signals to cables (transmission lines) by way of the bipolar ICs.